Voltage control device



Aug. 3, 1965 E. B. HILKER 3,199,020

VOLTAGE CONTROL DEvIOE Filed July 5, 1961 #fran/yin,

United States Patent O T his invention relates to electrical controldevices and more particularly to voltage control devices employingvariable impedances for control.

T he voltage of an electrical system is often controlled or regulated bya tap changing device associated with a tapped winding of a transformer;however, such equipment produces 'abrupt or stepped voltage changes.Variable impedances, such as saturable core reactors, have been used incontrol devices to vary or regulate voltage in a smooth or steplessmanner, but the cost of the impedances, especially when used in hiehervoltage systems, has been considerable. Also, some such saturable corereactor control arrangements produce undesirable phase shift etiectsbecause of their reactance, and in many cases, the saturation of thereactor cores produce undesirabiy high harmonic voltages in the system.

lt is therefore a general object of the present invention to provide avoltage control device employing Variable impedances and whichsubstantially avoids or overcomes to a large degree the abovementioneddisadvantages.

Another object of the present invention is to provide a variable voltageproducing control device employing variable impedances for control andwhich is especially economical.

Another object is to provide a volt-age control device employingsaturable reactors wherein the number of reactors and the cost of eachare substantially reduced.

Another object is to provide a voltage control device employingsaturable reactors for controlling the voltage of `a power supply systemin a stepless manner and wherein phase shift and harmonic effects areheld to a minimum.

Still another obgect is to provide a voltage control system employing aminimum number of saturable reactors in controlling the voltage of thesystem within `a relatively large control range while the electricaldesign ratings, and therefore cost, of the reactors is relatively low.

in accordance with one form of the present invention, a voltage controldevice is provided which includes a tirst circuit having a variableimpedance device, and a second circuit connected in parallel relationwith the first circuit and which includes another variable impedancedevice in series with a shiftable phase or reversible polarity source ofvoltage. By selectively varying the impedances, and changing the phaseor polarity of the voltage source, the voltage across the first namedimpedance can be varie-d over a substantial range.

These and other objects `and advantages of the present invention willbecome apparent from the following detailed description tal-:en inconjunction with the accompanying drawings.

in the drawings:

FlG. l is a schematic circuit diagram illustrating one embodiment of thepresent invention,

FlG. 2 is a graphical representation of the impedances of the controlledreactors of FG. 1 plotted as a function of supply voltage, and

Patented Aug. 3, i965 lCe FlG. 3 is a schematic circuit diagramillustrating another embodiment of the present invention.

The circuit of FlG l includes a pair of power input circuit terminalslil yand l?. connected across an alternating current supply source i4for supplying power to a load le through a transformer 1S having aprimary winding 2@ and a secondary winding 22 on a magnetic core 2.3.Connected in series circuit relation between the power input and outputcircuits is a voltage contr l device, indicated generally at Zd, forcontrolling the power output or load voltage within predeterminedlimits.

ln the illustrated embodiment shown in FIG. l, the voltage controldevice is connected between a pair of terminals 26 and Z3, and in serieswith primary winding 2li and the voltage supply source lli. rhe controldevice includes a variable impedance device shown as a saturable corereactor Sil having a reactance winding 32 and a control winding 34 on lamagnetic core 35. The rcactance winding 32 is connected between theterminals 2d and 2S in series with the supply source 11:- and primarywinding Ztl. Connected in parallel circuit relation with the reactor 3dbetween the terminals 25 and 23 is a series circuit including a variableimpedance, shown as a saturable core reactor 36, and an auxiliary sourceof voltage with means for reversing the polarity or vectorially shittingthe phase oi the voltage therefrom. The auxiliary source is shown inFlG. l as an auxiliary winding 3% on the core 23 connected with areversing switch 39, Reactor 36 includes a reactance winding iti andcontrol winding i2 on a magnetic core 443. The auxiliary winding 3S isconnected through the reversing switch 3% and the series connectedreactance winding d@ in a circuit across the reactance winding 32 ofreactor 33. A pair of terminals de' and 4d, which are respectivelyconnected to the opposite ends of winding 3S, are referred to herein asthe input terminals of the control device, while terminals 26 and 2S arereferred to as the output terminals of the control device.

The reversing switch 39 is shown for illustration as a two-positionswitch including a pair of movable contact arms 4S and which are movablein concert, as indicated by the dashed line connection 5l, and threestationary contacts S2, 5d, and 5d. ln the switch operating positionshown in HG. l, the contact arms 43 and Sd are in engagement withcontacts 52 and 5d, respectively. When the switch is actuated to itsother operating position, the contact arms f3 and 5@ are in engagementwith contacts 54 and 56, respectively. The stationary contacts 52 and 5oare connected together and they are connected by a lead d2 to one sideof the auxiliary winding 38. The center contact Sd is connected to theother side of winding 3S by a lead 45s, the reactance winding fait), anda lead 6o. With the switch 3% connected in this manner, the phase orpolarity connections of auxiliary winding 38 can be reversed withrespect to the terminals zo and 23.

The impedances ot the reactors and 3d are varied by passing controlcurrent through the reactor control windings 3d and 42 which varies thesaturation of the reactor cores 35 and lf-l. Wl ile various controlcircuits may be employed to supply control current to each of thecontrol windings and 42, simple, mechanically controllable, directcurrent sources, indicated generally at oil and 7?, are shown in thedrawings for illustration. The control source 68 includes a battery 72connected across a potentiometer which has a movable arm 76 connected toone side of the control winding 34, and one end of the potentiometer isconnected through and adjustable resistance 77 to the other side of thecontrol winding 3111. Similarly, the control source '70 includes abattery 7S connected across a potentiometer $0 having a movable arm 82connected to one side of control winding 42, and one end of thepotentiometer is connected to the other side of the winding 42 throughan adjustable resistor S3. The movable potentiometer arms 76 and S2 areshown coupled together for concert movement, as indicated by a dashedline connection Si.. As will be apparent from the circuit of FIG. l,movement of the potentiometer arms 76 and 32 to the left will decreasethe direct current in control winding 34 and increase the direct currentflowing in control winding 42. Movement of the potentiometer arms in theopposite direction or to the right will, of course, increase the currentin winding 3d and decrease the current in winding 52. In this way, thecontrol currents flowing in the reactor control windings can be variedinversely with respect to each other to thereby vary the reactances orreactance windings 32 and 40 inversely with respect to each other.

In the following discussion of the operation of the circuit of FG. l, itwill be assumed that the control device 24 is operated in a manner tomaintain the power output or load voltage substantially constant eventhough the voltage of supply source 14 varies above and below its normalor predetermined value. In describing the operation of the system, theauxiliary winding 38 is-considered as functioning as another secondarywinding to supply an input voltage Ei across the input terminals 45 andd6 of the control device 24 to thereby provide a variable phase adjustiny voltage e across the control device output terminals 26 and 2S. Bycontrolling the reactance values and selectively operating the reversingswitch 39, the voltage e can be varied so that it effectively aids oropposes the supply voltage Es, or is substantially ineffectual, tomaintain the power output or load voltage E at or return it to itspredetermined normal value. For purpose of illustration, the winding 38will be assumed to have a number of turns equal to of the number ofturns of primary winding 2 so that the voltage e between terminals 26and Z3 is effectively variable Within the range of from minus 10% toplus 10% of the normal value of supply voltage Es, as will be more fullyexplained hereinafter. In FIG. 2, curves X1 and X2, respectively,represent the impedance values of the reactance windings 32 and 40 ofsaturable reactors 30 and 36 over the voltage range of lcontrol device24. As indicated by curves X1 and X2, the 1mpedance of reactancewindings 32 and 40 are varied inversely with respect to each other. Whenthe supply voltage is at 100% of its normal value, the impedance ofwinding 32 is at a low or minimum value and the impedance of winding 430is at a high or maximum value. As the supply voltage decreases orincreases from its normal value, the impedance of winding 32, curve X1,increases while the impedance of winding 40, curve X2, decreases. Whenthe supply voltage is at 90% or 110% of its normal value, the impedanceof winding 32 is at a high or maximum value and the impedance of windingt0 is at a low or minimum value. The effects of varying the impedancesor reactors 30 and 36 will be more apparent from the following exampleof operation.

In considering the operation of the circuit of FIG. 1, the supply oivoltage ES and the load voltage EO will be considered to be at theirrespective normal values when the switch 39 is in the position shown inFIG. 1 and the potentiometers 74 and 80 are adjusted to provide a highor maximum DC. current in control winding 34 and a low or minimum DC.current in control winding 42. Under these conditions, reactor 301B willbe substantially saturated and the impedance of reactance winding 32 ata minimum value while the reactor 35 will be unsaturated and Cil theimpedance of winding 40 at a maximum value. Substantially all thecontrol device input voltage E1 will appear across the reactance winding40, and since the reactance of winding 32 is at a minimum value theadjusting voltage e will be substantially zero. The load voltage will beat its predtermined value as determined by the supply voltage value andturns ratio between the primary 20 and secondary 22. lf the impedance ofwinding 32 could be reduced to zero when the supply and load voltagesare at their normal values, there would be, in effect, a short circuitacross the terminals 26 an 28 and the adjusting voltage e would be zero.

If the supply Voltage Es increases from its normal value to a valueabove normal, the potentiometer arms 76 and S2 are moved to the left, asviewed in FIG. l, to thereby decrease the DC. current flowing in controlWinding 34 and increase the D C. current in control winding d2. Varyingthe control current in this manner increases the impedance of reactancewinding 32 and decreases the impedance of reactance winding 40. Anadjusting voltage e will now appear across reactance winding 32 andterminals 26 and 28, and will be in phase opposition with the supplyvoltage Es so that the load voltage E0 is maintained at or brought backto its normal value. For example, if the supply voltage ES increased to110% of its normal value, the impedance of winding 32 would be increasedto a high or maximum value and the impedance of winding 40 decreaesd toa low or minimum value so that the auxiliary winding 3S would supplysubstantially the full voltage E, (10% of the normal supply voltage)across terminals 26 and 28 in phase opposition or bucking relation withthe supply voltage Es. If the supply voltage now returns to its normalvalue, the potentiometer arms 76 and 82 are moved to the right to theiroriginal positions so that the adjusting voltage e is again at itsminimum or substantially zero value.

On the other hand, if the supply voltage decreases from its normalvalue, the switch 39 is irst operated to reverse the polarityconnections of auxiliary winding 3S to thereby vectorially shift thephase of the adjusting voltage e with respect to the supply voltage Es.By operating the switch from the position shown to its other position,input terminal 45 is connected through reactance winding 4t), contact54, and switch arm 4S to terminal 26, while input terminal 46 isconnected through Contact 56 and switch arm S0 to terminal 28. Theswitch is operated from one position to the other when the reactancewinding 32 is at a relatively low or minimum impedance value, thevoltage e being substantially at zero value and the supply and loadvoltages being substantially at their normal values. In this way,substantially all of the supply current is owing through reactancewinding 32 and substantially none through the switch when the switch isoperated.

After the switch 39 is operated as indicated above, the potentiometerarms are moved to the lett to increase the impedance of reactancewinding 32 and decrease the reactance of winding 4t). This againproduces an adjusting voltage e across terminals 26 and 2S but, underthese conditions, the voltage e is in aiding relation with the supplyvoltage Es to thereby maintain the load voltage E0 at or raise it to itsnormal value. It the supply voltage, for example, should decrease to ofits normal value, the impedance of reactance winding 32 is adjusted to ahigh or maximum value while the impedance of reactance winding 40 isdecreased to a minimum value to thereby provide an adjusting voltage ewhich is substantially 10% of the normal value of supply voltage andwhich is in the aiding or boosting direction.

While the circuit of FIG. 1 has been explained from a standpoint ofhaving the voltage e appearing across circuit terminals 25 and 28superposed on or injected into the supply voltage circuit in seriesaiding or opposing relationship, it can `be described, of course, fromthe standpoint of varying the effective ampere turns ascenso on theprimary side of transformer 13. From the latter point ot view, currentfrom supply source l-/s is considered to iiow through the auxiliarywinding in a direction relative to the direction of current in theprimary Ztl to provide variable aiding ampere-turns or opposingampere-turns dependinU upon the position of switch 39.

,l2-y utilizing the reversing Switch 3% to reverse the polarity orvcctorially shift the phase of the voltage impressed across the reactorEil, the same auxiliary windd can be used to provide both bucking andboosting voltage etlects, and only two reactors are necessary forproviding this control. Also, each of the reactors may be designed onlyfor the voltage of winding 33. For example, when either of the reactorsil@ and is saturated, the voltage across the other reactor issubstantially egual to that of winding 33 or the voltage Ei. Since thereactors may be designed only for the voltage Ot auxiliary winding 33,the voltage rating and size, as well as cost ot each reactor, isrelatively low.

ln addition, the total reactance in the power circuit of the system,i.e., the total series reactance presented by he reactors 30 and 36 isrelatively low. For example, en the supply voltage is at its normalvalue, in the stratcd example of operation, reactor Sil is at a very lowvalue, and when the supply voltage is at 90% and 110% of its normalvalue the other reactor 3d presents a low reactance to load currentflow. Because of the relatively low average reactance to load current7the passo shift between supply and load voltages is relatively low. Forthe same reason, harmonic voltages, often generated by core saturation,are relatively low in the circuit hereinbefore described.

While the control device input voltage E! in the illustrated embodimentis obtained from the auxiliary winding disposed on the same core withthe primary and secondary windings of transformer i3, other sources otvoltage may be used. For example, instead of auxiliary winding 3S, aseparate transformer may be employed having a primary winding connectedacross the load or supply source ld and a secondary winding connectedacross input terminals 45 and fit-6.

ln the rnodied construction shown in FlG. 3, a separate transformer lut)is utilized to provide the input voltage Ei to a control device.Transformer lli@ has a primary winding lo?, connected across a loadlliiand a secondary winding ldd connected to a pair of input terminalsindicated at 103 and llt) of a voltage control vice M2. The controldevice ll? is connected in series n cuit relation between a power supplysource lili and the load ldd.

The control device ll?. is sornes similar to the control device 2d inllG. l. As seen in FlG. 3, a saturand load ldd.

series with the secondary winding ldd, is connected between theterminals l2@ and i293 across th reactance winding i418. A reversingswitch lZS is connected between the winding No and the reactors forectorially shifting (180) the voltage from winding or input voltage Eiwith respect to the supply source voltage ES. When the reversing switchl is operated, it reverses the polarity connections of winding ldd andshifts the phase of the variable adjusting voltage e developed acrossterminals 12d and M2.

Reactors lid and lZ/l are provided with control windings E36 and 32,respectively, which are connected to be supplied with DE. controlcurrent for varying the impedance of their associated reactancewindings. As seen in FIG. 3, control windings i3@ and 132 are connectedto DC. control sources 13d and 136, respectively. Each ot the controlsources are shown as including potentionieters and batteries with thearms of the potentiomw eters interconnected for concert movement, as inthe circuit of l.

The operation of the circuit ot FlG. 3 is similar to that described inconnection with the circuit of FIG. l. By varying the currents incontrol windings 13@ and 132 inversely with respect to each other, theimpedances of reactance windings ll and E25 vary inversely with respectto each other to thereby vary the adjusting voltage e across terminalsl2@ and i221. The adjusting voltage e is combined with the supplyvoltage Es to control or regulate the load voltage E0. As previouslymentioned herein with regard to the circuit of FIG. l, the variableadiusting voltage e can be controlled to provide a voltage boosting or avoltage bucking effect depending upon the position of trie reversingswitch. The impedances ot reactance windings llo and d may be varied inthe manner shown in FIG. 2. in such case, the curve X1 would representthe impedance values of winding il@ and curve X2 the impedance values ofwinding 126 over the voltage control range of the control device. Theswitch llt? is operated from one position to its other position when thereactance of winding MS is low or at a minimum value and is carryingsubstantially the full load current.

While the voltage control device in each of the illustrated einoodiin "sis conductively coupled into the power circuit by dn ect connection, acoupling transformer (not shown) may be used. ln such case, the primaryof the coupling transformer may be connected across the reactor Si? inFIG. l, or the reactor M6 in FlG. 3, and the secondary connected inseries in the power circuit.

it is to be understood that the foregoing description and theaccompanying drawings have been given only by way of illustration andexample, and that changes and alterations in the present disclosure,which will be readily a, arent to one si led in tlc art, arecontemplated as within the scope of the present invention which islimited only by the claims which follow.

What is claimed is:

l. A voltage control device comprising a tirst circuit including a iirstvariable impedance device, a second circuit coupled across said rstcircuit and including a second variable impedance device, means forconnecting a source of voltage in said second circuit to provide avoltage across said lirst circuit, means for selectively reversing thephase of said voltage, and means for varying the impedance values ofsaid impedance devices to vary the magnitude of said voltage.

Z. A voltage control device comprising a first variable impedancedevice, a series circuit including a voltage source and a secondvariable impedance device coupled in parallel circuit relation with saidfirst impedance device, means for inversely varying the impedance valuesof said impedance devices to provide a variable voltage across rstvariable impedance device, and means operable to reverse the phase ofsaid variable voltage.

3. in combination, a power output circuit, a power input circuitconnected to a lirst source of supplyl voltage to supply power to thepower output circuit, and a voltage control device for varying thevoltage supplied to said power output circuit comprising a firstvariable impedance device coupled in series circuit relation with one ofsaid power circuits, a series circuit including a second variableimpedance device and a second source of voltage coupled in parallelcircuit relation with said first impedance device, means for varying theimpedance values of said impedance devices to provide a variable voltageacross said iirst impedance device, and switch means in said seriescircuit for selectively connecting said second source ot voltage ineither aiding or opposing relation with respect to the voltage of saidfirst source `of voltage.

d. A voltage control device comprising a irst circuit including a firstvariable impedance device, a second Sill u circuit connected across saidfirst circuit and including a second variable impedance device, meansfor connecting a source of voltage in said second circuit, means forvarying the impedance values of said devices to provide a variablevoltage across said first impedance device, and a mechanical reversingswitch connected said second circuit for selectivity reversing the phaseof said variable voltage.

5. A voltage control device comprising a first variable reactance devicedevice, a series circuit including a transformer winding and a secondvariable reactance device coupled in parallel circuit relation with saidiirst reactance device, means for energizing said winding to providevoltage of predetermined phase in series circuit, means for varying thereactance values of said reactance devices, and means for shitting thephase or said voltage lSO".

6. A voltage control device comprising a pair ot saturable reactors eachhaving a reactance winding and a control winding, a series circuitincludingT a source of voltage of predetermined phase and the reactancewinding of one of said reactors, said series circt t being coupled inparallel circuit relation with the reactance winding of the other ofsaid reactors, means for supplying variable control current to each ofthe control windinUs of said reactors to provide a variable voltageacross the reactance winding of said other reactor, and additional meansoperable to shift the phase of said variable voltage.

7. An electrical system comprising a power input circuit connectable toa source of supply voltage for supplying power to a power outputcircuit, a iirst circuit including a iirst saturable reactor coupled inseries circuit relation with one of said power circuits, a secondcircuit including a second saturable reactor coupled in parallel circuitrelation with said first circuit, means for connecting an auxiliarysource of voltage of predetermined phase in said second circuit, meansfor Varying the reactance values of said reactors inversely with respectto each other, and additional means for shifting the phase of thevoltage from said auxiliary source with respect to said supply voltage.

8. An electrical control device comprising a iirst circuit including aiirst saturable reactor, a second circuit including a second saturablereactor and a transformer winding connected in series, said secondcircuit being coupled across said rst circuit, means for varying thereactances of said first and second reactors, and a mechanical reversingswitch connected in said second circuit for selectively reversing thephase connections of said winding.

9. An electrical system comprising a power input circuit connectable toan alternating current source of supply voltage for supplying power to apower output circuit, a first saturable reactor coupled in seriescircuit relation between said power circuits, a series circuit includinga transformer winding and a second saturable reactor coupled in parallelcircuit relation with said iirst saturable reactor, means for energizingsaid winding to provide a voltage across said iirst saturable reactor, amechanical reversing switch in said series circuit operable to reversethe phase conne tions of said winding in said series circuit, and meansfor varying the reactance values of said reactors.

it). An alternating current supply system comprising power input andoutput circuits, a transformer having a main winding coupled across oneof said power circuits, and an auxiliary winding coupled to said mainwinding, and a control circuit comprising a irst circuit including aiirst reactor coupled in series with said main winding, a second circuitincluding a second reactor connected in series with said auxliarywinding, and a reversing switch for selectively reversing the phase ofthe voltage from said auxiliary winding, said second circuit beingcoupled in parallel relation with said rirst circuit, and

Si means associated with said reactors for varying the reactancethereof.

it. An alternating current control system comprising a transformerhaving a main primary winding connected to an alternating current supplysource, a main secondary winding connected to a load circuit, and anauxiliary winding, and a voltage control device comprising a iirstcircuit including a irst saturable reactor coupled in series circuitrelation with one of said main windings, a second circuit including asecond saturable reactor and said auxiliary winding connected in seriestherewith, said second circuit being connected in parallel circuitrelation with said first circuit, a reversing switch connected with saidauxiliary winding for selectively reversing the phase relationship ofsaid auxiliary winding with respect to said primary winding, and meansfor inversely varying the reactances of said reactors.

l2. An A.C. power supply system comprising power input and outputcircuits, means for connecting said power input circuit to an A.C.voltage supply source for supplying power to said power output circuit,and a voltage control circuit for controlling the voltage supplied tosaid power output circuit comprising a iirst saturable core reactorhaving a reactance winding and a control winding, a rst circuit havingend terminals and including the reactance winding of said iirst reactorconnected between said end terminals, means connecting said iirstcircuit in series circuit relation with said power input and outputcircuits, a second circuit including a second saturable core reactorhaving a reactance winding and a control winding, an auxiliary A.C.voltage supply source, and means including a phase reversing switchhaving tirst and second switch positions connecting the reactancewinding of said second reactor in series circuit relation with saidauxiliary source across said iirst circuit between said end terminals,said switch when in said iirst switch position connecting one of saidend terminals through the reactance winding of said second reactor toone side of said auxiliary source and the other of said end terminals tothe other side of said auxiliary source, said switch when in said secondswitch position connecting said one end terminal to said other side ofsaid auxiliary source and said other end terminal through the reactancewinding of said second reactor to said one side of said auxiliarysource, means for supplying control current to each of said controlwindings, and means for inversely varying the magnitudes of the controlcurrents iiowing in said control windings for inversely varying thereactance values of said reactance windings to provide a variable A.C,voltage across said iirst circuit.

13. An A.C. power supply system comprising a power input and outputcircuits, means for connecting said power input circuit to an A.C.voltage supply source for supplying power to said power output circuit,and a voltage control circuit for controlling the voltage supplied tosaid power output circuit comprising a first saturable core reactorhaving a reactance winding and a control winding, a iirst circuit havingfirst and second circuit terminals and including the reactance windingof said first reactor connected between said circuit terminals, meansconnecting said iirst circuit in series circuit relation with said powerinput and output circuits, a second circuit including a second saturablecore reactor having a reactance winding and a control winding, atransformer having a transformer winding with end terminals, means forenergizing said transformer winding to provide a voltage thereacross,and means including a phase reversing switch having iirst and secondswitch positions connecting the reactance winding of said second reactorin series circuit relation with said transformer winding across saidiirst circuit between said circuit terminals, said switch when in saidiirst switch position connecting said iirst and second circuit terminalsto said first and second end terminals, respectively, with the reactancewinding of said second reactor connected between one of said circuitterminals and one of said end terminals, said switch when in said secondswitch position connecting said rst and second circuit terminals to saidsecond and rst end terminals, respectively, with the reactance windingof said second reactor connected between one ot said circuit terminalsand one of said end terminals, means for supplying control current toeach of said control windings, and means for inversely varying themagnitudes of the control currents owing in said control windings forinversely varying the reactance values of said reactance windings toprovide a variable voltage across said tirst circuit to control thevoltage supplied to said power output circuit.

No references cited.

LLOYD MCCOLLUM, Primary Examiner.

ROBERT C. SIMS, Examiner.

1. A VOLTAGE CONTROL DEVICE COMPRISING A FIRST CIRCUIT INCLUDING A FIRSTVARIABLE IMPEDANCE DEVICE, A SECOND CIRCUIT COUPLED ACROSS SAID FIRSTCIRCUIT AND INCLUDING A SECOND VARIABLE IMPEDANCE DEVICE, MEANS FORCONNECTING A SOURCE OF VOLTAGE IN SAID SECOND CIRCUIT TO PROVIDE AVOLTAGE ACROSS SAID FIRST CIRCUIT, MEANS FOR SELECTIVELY REVERSING THEPHASE OF SAID VOLTAGE, AND MEANS FOR VARYING THE IMPEDANCE VALUES OFSAID IMPEDANCE DEVICES TO VARY THE MAGNITUDE OF SAID VOLTAGE.